Optical sensors to obtain optical signals representative of physical processes and events within the combustion chamber of IC engines have been previously proposed. The optical signals are conducted by light guides to optical-electrical transducers to obtain corresponding electrical signals which, then, can be utilized to control operation of the IC engine. Such a utilization apparatus may, for example, include a control system to recognize knocking or pinging operation of the engine, and to then control the engine so that knocking or pinging operation is prevented.
Optically sensing combination events within the combustion chamber of an IC engine places rigorous demands on the optical pickup which must be exposed, physically, to the combustion conditions. The referenced earlier U.S. application Ser. No. 06/314,651, assigned to the assignee of the present application, and the disclosure of which is hereby incorporated by reference, describes a sensor which has a window made of quartz glass located at the combustion chamber of the IC engine, the quartz glass window being coupled to a light guide cable to conduct optical signals to the sensor element terminal remote from the combustion chamber. It has been found that extended use of such a sensor, particularly under operating conditions involving extremely high temperatures may cause damage to the quartz glass window, since quartz glass, although very resistant to high temperature, is not sufficiently sturdy to withstand the extremes of temperatures to which it may be exposed in the combustion chamber of some IC engines.